The automation of a work machining system, i.e., that known as FA (factory automation), has been widely disseminated. The automated work machining system grips a work to be machined, with a gripping device attached to the extremity of the robot hand i.e., an end effector, of an industrial robot, transports the work, feeds the work to an automatic machine tool, such as an automatic lathe or a machining center, and grips the machined work with the gripping device to transport the processed work. Generally, a workshop of an FA system has a work feed station provided with work feed means for feeding work successively to the robot hand of an industrial robot and for receiving the machined work from the robot hand to efficiently handle and process many pieces of work. In most cases, such a work feed means is called a work feeder. The work feeder comprises an intermittently turning base or a circulating device, and a plurality of pallets mounted on the intermittently turning base or the circulating device. The pallets each holding a plurality of work in a stack are located sequentially at a work transfer position. The industrial robot picks up one of the stacked work from the work feeder at the work transfer position, attaches the work to the spindle of an automatic machine tool, i.e., the chuck of the automatic machining tool, and returns the machined work to the empty pallet of the work feeder. The work feeder is replenished with fresh work, and delivers machined work therefrom in accordance with a progress of an automatic machining process.
FIG. 10, 11 and 12 are schematic views of the layout of a conventional industrial robot and a conventional work feeder, and the construction of a pallet and work support rods of the conventional work feeder.
Referring to FIGS. 10, 11 and 12, the industrial robot 1, of the prior art, has a robot body 2, a first robot arm 3 extending from the robot body 2, and a second robot arm 4 pivotally joined to the first robot arm 3. A robot hand 5, i.e., an end effector, is attached to the extremity of the second robot hand 4, and two work grippers 6 are held on the robot hand 5. The first robot arm 3 is capable of both turning and extended. The first robot arm 3 and the second robot arm 4 can be turned together in directions indicated by an arrow P. A work feeder 8 has a base 9, and a plurality of pallets 10 mounted on the base 9. As shown in FIG. 11, each pallet 10 has a work support plate 11 and is provided with a plurality of work support rods 12 for holding work in place on the work support plate 11. The pallets 10 are moved on the base 9 via a work lifter 13 disposed near a predetermined work transfer station.
A plurality of work is held in a stack on each pallet 10 of the work feeder 8 combined with the industrial robot 1, and the pallets 10 are moved sequentially via the work transfer station near the work lifter 13. When the pallet 10 is located at the work transfer station, the work gripper 6 of the robot 1 approaches the work, and grips and lifts up the same. Then, the work gripper 6 is moved away from the work feeder 8 by a motion indicated by the arrow P, and the work is fed to the machining stage of an automatic machining tool such as the spindle of an automatic lathe, not shown, by the turning and linear motions of the first robot arm 3. On the other hand, when the work feeder 8 receives a machined work from the automatic lathe, the machined work is moved away from the spindle of the automatic lathe by the turning and linear motions of the first robot arm 3, and the work gripper 6 approaches the work feeder 8 to return the machined work to an empty one of the pallets 10 of the work feeder 8.
A series of the foregoing operations is carried out according to a predetermined program.
It is understood from considering the actions of the conventional work feeder 8 and the industrial robot 1 that the work lifter 13 of the work feeder 8 functions in gripping the uppermost work among work stacked on the pallet 10 with the work gripper 6 held on the robot hand 5 of the industrial robot 1, to insert a lifting fork accommodated in the work lifter 13 to a space under the work support plate 11, and to lift up the work support plate 11 to place the work on a level corresponding to the upper ends of the work support rods 12 so that the work gripper 6 held on the robot hand 5 is able to easily grip the work. Such an operation of the work lifter 13 is needed because the work support rods 12 are set upright, the length of portions of the work support rods 12 extending upward from the work support surface 11 of the work support plate 11 is fixed, although the work support rods 12 have mounting studs 12a slidably seated on the inner bottom surface of the pallet 10 so that the work support rods 12 are radially movable along cross-shape slots (FIG. 11) formed in the work support plate 10a, depending on the size of works as shown in FIG. 12, the work rods 12 interfere with the movement of the robot hand 5 if the work gripper 6 held on the robot hand 5 is moved toward the uppermost work only by the longitudinal movement of the first robot arm 3, and thus the work gripper 6 is unable to reach the uppermost work.
The use of such a work lifter in the automated machining workshop and timing the operation of the work lifter 13 in synchronism with the work transfer operation of the industrial robot 1 requires a complicated programmed operation for carrying out the automatic machining, and the work can be transferred between the robot 1 and only the pallet 8 located at a position in alignment with the work lifter 13, because the work lifter is essential to the transfer of the work between the industrial robot 1 and the pallet 10. Furthermore, since the disposition of the work lifter 13 is limited when installing the work feeder 8 in the automated machining workshop, there are many restrictions on the disposition of the work feeder 8 relative to the automatic machining tool and the industrial robot.